Blow torch feeder control



March 14, 1961 J THOMAS ET AL 2,975,002

BLOW TORCH FEEDER CONTROL 2 Sheets-Sheet 1 Filed March 14, 1960 INVENTORS JOHN R KARPUK JESSE B. THOMAS JIQZ March 14, 1961 J. B. THOMAS ETAL 2,975,002

BLOW TORCH FEEDER CONTROL Filed March 14, 1960 2 Sheets-Sheet 2 INVENTORS JOHN E KARP JESSE B. THO

-up and suspend the powder. variations may result which invite flash back and its.

United States Patent- Q BLOW 'roncn FEEDER CONTROL Jesse B. Thomas, Henrico County, Va., and John P.

' Karpuk, 'Middlesex- County, Mass, assignors to Reynolds Metals Company, Richmond, Va., a corporation ofDelaware Filed Mar. 14, 1960, Ser. No. 14,659

2 Claims. (Cl. 302-50) The present invention relates generally to blow torch apparatus for burning powdered metals, and, more particularly, to a fuel feeding means for mixing a stream of metal powder with a stream of oxygen to form a composite fuel stream which is to be burned in a blow torch. This application is a continuation-in-part of our copending US. application, Serial No. 437,438, filed June 17, 1954, now Patent No. 2,939,410 granted June -7, 1960.

It is conventional to burn highly exothermic metal powders, such as aluminum powder, in a suitable blow torch to produce high cutting-flame temperatures. A blow torch of this type, which burns metal powder in a field or zone of oxygen, is especially suited for "use in cutting through refractory materials'.' But these torches can also be dangerously difficult to control. For safe effective operation with a given rate of metal powder 2,975,002 Patented Mar. 14, 1961 speed of the worm and the rate of flow of the oxygen be ng suitably correlated to maintain a predetermined mixture proportion. The metal powder is supplied to the worm from a suitable storage chamber or hopper, and if desired, an agitator may be provided to prevent bridging of the power in the hopper. The flow of oxygen through the screw against the direction of feed of feed, the gas flow velocity must have (1) a low limit which is equal to or possibly somewhat higher than the rate of, flame propagation so as to prevent flash back, (2) a high limit which is low enough to avoid blowing away and thereby extinguishing the flame and (3) an ability, between these limits, to pick up the metal powder fast as it is fed to the stream and to maintain that powder in suspension from the pick-up area to the flame. While it is generally easyenough to maintain the gas flow at a steady value within its proper limits, difiiculty has heretofore been encountered in maintaining the powder flow at a uniform feed rate. Where the feed is erratic, there is the possibility that the maximumfeed rate may exceed the ability of the gas stream to pick As a consequence, gas flow attendant dangers.

This invention has, for one of its important objects,

containing oxygen and metal powder in a substantially uniform proportion or ratio.

Another object is the provision of an apparatus for maintaining a flow of metal powder to and mixing it with ,a stream of oxygen in a manner which minimizes the possibility of flash backs and correspondingly avoids the dangers incidental thereto.

Another object is the provision of a feeding apparatus for introducing metal powder into an oxygen stream which will operate steadily for long periods without deterioration.

Another object is the provision of an apparatus arranged to prevent accumulations of metal powder in theoxygen line.

' Another object is the provision of such an apparatus which is of simple construction and is easy to operate the powder is prevented by providing oxygen pressure in the hopper slightly higher than the oxygen pressur at the mixing point of oxygen and metal powder.

Mixing of the metal powder and oxygen is accomplished by introducing the oxygen directly into the powder feed screw chamber. The accumulation of metal powder in the bearing of the feed screw is prevented by providing a higher oxygen pressure in the bearing than the pressure in the feed screw chamber, so that powder will not flow or drift from the chamber into the bearing, These last two steps are conveniently and economically carried out bycombining the oxygen inlet or bearing gland means of the feed screw bearing with the oxygen inlet into the feed screw chamber for powder mixing purposes.

The invention will be described in greater detail in connection with the accompanying drawing illustrating a preferred embodiment of the invention by way of example, and wherein: Fig. 1 is an elevational view showing the blow torch and its associated apparatus;

Fig. 2 is a side elevational view of the powder feed ing cabinet, with parts broken away;

Fig. 3 is an enlarged longitudinal section of the I powder feeding mechanism shown in Fig. 2; and

Fig. 4 is an enlarged section taken on lines 4-4 of Fig. 3.

General apparatus stream and other accessory equipment, valves and controls necessary for operating the torch 1. Oxygen is suppliedto the cabinet 8 from a bottle or tank 9 through an oxygen conduit 10 and igniter gas is supplied from a bottle or tank 11 through a conduit 12.

Briefly, in operating the above apparatus, the oxygen supplied from the bottle 9 to the cabinet 8 flows through a control valve in the cabinet and is mixed with metal powder in the cabinet. The resulting mixture then flows through the conduit 3 to the blow torch 1. A suitable valve means in the cabinet controls the flow of igniter gas from the bottle 11 through the conduits 12 and 4 to'the blow torch 1. For a specific description of 'the construction and operation of this apparatus, reference may be made to our afore-mentioned US. application, Serial No. 437,438.

Powder feeding and mixing cabinet The present invention is particularly concerned with the powder mixing cabinet 8 and the means in the cabinet for mixing the metal powder with the oxygen stream. The cabinet 8, shown in Fig. 2, is generally a box-like structure and includes four sidewalls 14, a bottom wall 15 and a top wall 16. Casters 17 are mounted on the bottom wall 15 for supporting the cabinet. The top wall 16 includes an opening therein receiving a conically shaped hopper 18 for holding a supply of powdered metal, such as powdered aluminum. The hopper 18 includes a removable cover at its top for filling it.

The bottom of the hopper 18 includes a flange 20,surrounding its discharge opening. This flange is secured to a corresponding flange at the top of a feed screw housing 21, which has an integrally secured fitting 21 a extending horizontally from its bottom end portion. The housing 21 contains an upwardly open passageway or powder inlet 22 which communicates, at its upper end with the discharge opening of the hopper 18 to receive powder therefrom.

As seen in Fig. 3, the housing 21 includes a feed screw chamber 23 having an inlet end section i, corresponding to the bottom of the powder inlet passageway 22, an outlet or discharge end section d and an interconnecting mid-section m, the discharge and midsections being located in the fitting 21a. A horizontal feed screw 24 is mounted in the chamber 23 to receive metal powder at the inlet section 1' and convey it through the mid-section m into the outlet section a'." The outlet end of the feed screw 24 is axially aligned with and connected to a drive shaft 25 which extends through and projects from the outer end portion of the fitting 21a.

At the point where the shaft 25 emerges from the outer end of the fitting 21a, a stufling box 26 of conventional construction is arranged to surround the shaft. The box 26 is connected, by suitable means such as screw threads, to the feed screw housing. The drive shaft 25 is driven through a coupling 27 and a reduction gear 28 by a motor 29. The rotary speed of the feed screw 24 determines the feeding rate of the metal powder; hence, the reduction gear 28 and motor 29 are selected to provide the screw 24 with the proper rotary speed.

A plug or sleeve 31 is placed in the outer end portion of the fitting 21a, between the outlet section d of the feed screw chamber 23 and the box 26. It has a central bore 32 through which the feed screw drive shaft 25 extends. The periphery of the plug 31 is provided with an annular groove 33 intermediate its ends. It is further provided with several axially extending and anguiarly spaced grooves 34 extending from the annular groove 33 to the inner end 35 of the plug 31. This innerend 35 forms the outer end wall of the discharge section d of the feed screw chamber 23. Several angularly spaced radially extending passages 36 extend inwardly from the floor of the annular groove 33 to the bore 32.

A stream .of oxygen is introduced into the annular groove 33 through a passage 38 provided in a downward extension of the outer end portion of fitting 21a on the feed screw housing 21. The passage 38 is connected to an oxygen supply pipe 39, which receives oxygen from an oxygen supply bottle 9 and which is connected to pipe 39 through the conduit and other cabinet means that oxygen is normally admitted to the inlet passage 38 prior to energizing the feed screw motor 29. The oxygen flows through the passage 38 to the annular groove 33 where it divides into a major portion flowing along the unrestricted axial grooves 34 into the screw chamber 23 and a relatively small portion flowing through the radial passages 36 to the plugs bore 32 and along the very restricted passageway provided between the adjacent walls of the shaft and the bore 32 and extending into the outlet section of the chamber 23. The oxygen flow then leaves the chamber 23 via the outlet passage 44 and flows to the blow torch 1 through the outlet pipe 45 and conduit 3. Up to this point, only oxygen is exiting from the chamber as the feed screw 24 is stationary.

When it is time to start a mixture of oxygen and metal powder flowing to the blow torch 1, the motor 29 is energized and drives the screw 24 at a controlled rate to convey powder from the powder inlet 22 of the housing-21 toward the outlet passage 44. As the powder ap' proaches the outer end of the feed screw chamber 23, the streams of oxygen issuing from the axial grooves 34 in the plug 31 pick up and mix with the powder particles to form a suspension of the powder in the are not shown in the drawing. Fig. 2 shows the oxygen supply passage 38 as also being connected to a pipe 42, which communicates with the space in the top of the hopper 18 over its charge of powder, and to a pipe 43, which communicates with a pressure control switch (not shown) forming part of the controls for the torch operation.

A powder mixture outlet passage 44 is formed in the upper side of the fitting 21a. It accommodates the discharge of the powder-suspending gas stream from the discharge section d of chamber 23. The passage 44 is connected by an outlet pipe 45 to the conduit 3 leading to the blow torch 1.

Operation The full operation of the entire apparatus is described in our aforementioned US. application Serial No. 437,- 348. The following description is confined to the operation of the powder feeding means described above.

In starting the operation of the powder feeding means,

oxygen and the resulting mixture streams out the outlet passage 44 to the torch 1.

The minor amount of oxygen flowing through the radial passages 36 and the bore 32, along the drive shaft 36, to the screw chamber 23 keeps powder from being carried along the drive shaft in the opposite direction, and, after exiting into the chamber, further adds to the oxygen metal powder mixture.

The mixture of metal powder and oxygen flowing to the blow torch 1 is stopped by deenergizing the feed screw motor 29. Normally, thereafter, after all the metal powder is blown from the lines, including the pipe 45 and the conduit 3, the oxygen flow is stopped by closing a valve (not shown) delivering oxygento the oxygen supply pipe 39.

Having described our invention, we claim:

1. A metal powder and gas mixing apparatus for a blow torch comprising: a feed screw housing containing a feed screw chamber having laterally spaced inlet and outlet end sections separated by an interconnecting midsection; a hopper connected to said housing for supplying metal powder to the inlet end section of said chamber; a metal powder feed screw in said chamber for conveying metal powder from the inlet end section through the mid-section to the outlet end section, said feed screw having a drive shaft adjacent said outlet end section; a sleeve having a bore containing a portion of said drive shaft, said sleeve having a transversely extending arcuate groove in its outer periphery; means forming a gas 'inlet in said housing leading to said groove; means forming axial openings along said sleeve for conducting a stream of gas from said groove to said outletend section where said gas stream picks up and suspends said metal powder; and an outlet from said outlet end section for discharging a stream of said powder-suspending gas from said screw chamber.

2. The apparatus of claim 1 including: a radially extending passage in said sleeve extending between said peripheral groove and the bore of said sleeve to conduct oxygen to said drive shaft to prevent the discharge of metal powder from said chamber through said bore.

References Cited in the file of this patent UNITED STATES PATENTS 1,772,244 Crite's Aug. 5, 1 930 1,872,028 Collins Aug. 16, 1932 2,448,745 Struckmann Sept. 7, 1948 2,841,101 Hale July 1. 1958 

